Arrangement for automatic switching systems



Dec. 27, 1966 J. L. DE KROES ETAL 3,294,920

ARRANGEMENT FOR AUTOMATIC SWITCHING SYSTEMS 2 Sheets-Sheet 1 Filed May6, 1963 U iiwiiwili 1 m m c T v M B M M M u M M M W1 J. M. F% M .Z/M. MM M M M n, M M M 1 1 h H M m |||||L| m W IIII WMAM A 2 A 1m m Mm m m n mm M M M M M M MM??? M /M M i M m 2 W H m H 2 K H 1 L M M M M M M M M V pm lllL .IIIIL M IIIIIL IIIIIL M m M m W WIgIVENTORS TJfi RKO M.SCHURINGA A GENT 7, 1966 J. DE KROES ETAL 3,294,920

ARRANGEMENT FOR AUTOMATIC SWITCHING SYSTEMS Filed May 6, 1963 2Sheets-Sheet 2 BC(p,s,t) KC ,d,1,p) CD(s,d,?) m ows d n) BCm m UnitedStates Patent 3,294,920 ARRANGEMENT FOR AUTOMATIC SWITCHING SYSTEMS JanLouis de Kroes, Willem Smit, and Tjakko Marinas Schuringa, Hilversum,Netherlands, assignors to North American Philips Company, Inc, New York,N.Y., a corporation of Delaware Filed May 6, 1963, Ser. No. 278,035Claims priority, application Netherlands, May 4, 1962, 278,092 2 Claims.(Cl. 179-18) This invention relates to arrangements for automaticswitching systems, for example telephone systems, comprising first andsecond groups of conductors and a plurality of sequential switchingstages located between the two groups of conductors and connectedtogether by groups of intermediate conductors located between each twosequential switching stages. At least one connecting path exists betweeneach conductor of one group and each conductor of the other groupthrough .a seriescombination of intermediate conductors, comprising oneintermediate conductor of the intermediate conductors located betweeneach two sequential switching stages.

An object of the invention is to provide an arrangement of the abovekind in which the switching stages include crosspoint switches havingrelay contacts at the crossings between two groups of relativelyparallel conductors. The relay contacts are located between theconductors and are controlled by relays. The arrangement is very simpleand needs a minimum number of relay windings and relay contacts percrossing.

According to the invention each switching stage in cludes a plurality ofcrosspoint switches, a seriescombination of a unidirectionallyconductive element and a relay winding, included between a marking.conductor and either an intermediate conductor connected to thepreceding switching stage, or a conductor of the first group, beingassociated with each crosspoint. The common point between theunindirectionally conductive element and the relay winding is connectedthrough a contact of the relevant relay to either an intermediateconductor connected to the next switching stage, or a conductor of thesecond group. A marker is connected to the marking conductors and to theconductors of the first group for selecting a free connecting pathbetween a given conductor of the first group and a given conductor ofthe second group through free intermediate conductors. The markerapplies, for marking the selected connecting path, a marking voltage tothe relevant conductor of the first group and to the marking conductorswhich are connected through the series-combination of a unidirectionallyconductive element and a relay winding to either the intermediateconductors located in the selected connecting path, or the givenconductor of the first group, so that the relays the windings of whichare included in the selected connecting path are successively energized.The conductors of the second group are connected through a path having asmall direct-current resistance to a point of constant potential and,after closure of the relay contact connected to the given conductor ofthe second group, a voltage being applied to the given conductor of thefirst group such that the voltage of the given conductor of the firstgroup and of the intermediate conductors decreases below the markingvoltage of the marking conductors connected to said conductors throughthe series-combination of a unidirectionally conductive element and arelay winding and the relays thus keep energized.

In order that the invention may be readily carried into effect, it willnow be described in detail, by way of 3,294,920 Patented Dec. 27, 1966example, with reference to the accompanying diagrammatic drawing.

FIGURES 1 and 2 are to be placed side by side.

The arrangement according to the invention as shown in FIGURES 1 and 2forms part of a network of connections used in an automatic telephoneexchange and which serves to establish connecting paths between interalia subscribers line circuits, on the one hand, and output, input andlocal repeaters and registers or centralized devices of other kind, onthe other hand. Said connecting paths usually extend through a pluralityof wires or conductors, namely through the line wires (aand b-wires) andthrough one or more control or signalling conductors (c, d etc. wires).The figures show only the portion of the network relating to the controlof the network, namely the portion relating to the building up andholding of a connecting path. A connecting path is built up by means ofa control conductor (c-wire) extending parallel to the line wires andwhich also serves to hold and interrupt the connecting path. The linewires are switched through via contacts of the same relays as is thecontrol conductor so that the network of telephone connections extendsin parallel and is built up in quite an .analogus manner as the controlposition of the communication etwork. If desired, additional conductors,for example for the tax indication or four-wire transmission, may be putthrough.

It is naturally impossible for the network of connections employed in anautomatic telephone exchange to be shown completely and this is by nomeans necessary for explaining the present invention. The figures showthe arrangement according to the invention only in a greatly reducedform, the aim having been to minimize the number of frames, the numberof switches per frame and the number of crossings per switch which arerequired for the explanation of the invention. Thus, FIG- URES 1 and 2show in detail the portion of a fictive automatic telephone exchangerelating to the control of the communication network for eightsubscribers and eight repeaters or registers. This arrangement makes itpossible for the advantages of the invention to be explained in a simplemanner.

The arrangement shown in FIGURES l and 2 comprises two primary frames LFand LF each having connected to it four subscribers line circuits LS,and two secondary frames TF and TF to each of which four repeaters OVare connected. It is to be noted that switching elements of the sametype are indicated by the same. denomination and that, in order todistinguish between switching elements of the same type, thisdenomination is followed by one or more indices. The line circuit LS isthus an arbitrary one of the line circuits LS LS LS A primary frame LFincludes two A-switches and two B-switches, each A-switch in eachprimary frame being connected through one AB- conductor (link) to eachB-switch. The line circuits LS are connected to the A-switches orprimary switches which are connected through the AB-conductors to theB-switches or secondary switches. A secondary frame TS includes-twoC-switches and two D-switches, each C-switch in a secondary frame beingconnected through one CD-conductor to each D-switch. The repeaters areconnected to the D-switches or secondary switches which are connectedthrough the CD-conductors to the C-switches or primary switches.

Between each primary frame LF and each secondary frame TF a plurality ofconnecting paths are possible each extending through one BC-conductor(junctor). In fact, each primary frame LP is connected through twoBC-conductors to each secondary frame TE. To this end, each B-switch ina primary frame is connected through a BC-conductoi" to one C-switch ineach secondary frame. Thus between a given line circuit LS and a givenrepeater OV a plurality of connecting paths are possible each extendingthrough one AB-conductor, one BC-conductor and one CD-conductor, thenumber of connecting paths possible being equal to the number ofBC-co'nductors between the primary and secondary frames.

I Each switch comprises two groups of relatively parallel connectingpaths which cross one another at four crossings, only one conductor ofeach connecting path, namely the control conductor (c-wire), beingshown. Said groups are referred to for distinction as the vertical groupand the horizontal group. The vertical .group is shown in the verticaldirection and the horizontal group in the horizontal direction. Forexample, the line circuits LS are connected to the vertical groups ofthe A-switches and the AB-conductors are connected to the horizontalgroups of the A-switches and to the vertical groups of the B-switches.Each .group includes two control conductors so that each conductor ofthe horizontal group may be connected to two conductors of the verticalgroup.

In practice a network of connections for an automatic telephone exchangemay have, for example, 4,600 subscribers and 800 repeaters or registers.A communication network for such a telephone exchange comprises, forexample, ten primary frames LF each including ten A-switches and tenB-switches, an A-switch having 40 connections in a vertical group andten connections in a horizontal group. The number of subscribersconnections in each primary frame is then 400 and for the ten framestogether 4,000. The B-swi-tches have ten connections in a vertical groupand ten connections in a secondary group. The number of AB-condnctors ina primary frame is thus 100 and 100 BC-conductors are connected to aprimary frame. The network also comprises ten secondary frames TF eachincluding ten C- switches and ten D-switches, a C-switch having ten onnections in a vertical group and ten connections in a horizontal group.The number of BC-conductors connected to a secondary frame is then 100so that each primary frame is connected to each secondary frame throughten BC-conductors. A C-switch has ten connections in a vertical groupand eight connections in a horizontal group. The number of CD-conductorsin a secondary frame is thus 100 and the number of repeater connectionsper secondary frame is 80 and for the secondary frames together 800.

A given connecting path through the communication network ischaracterized by a plurality of indices, namely:

(p), the number of the primary frame,

(a), the number of the A-switch in the primary frame,

(m), the number of the connection in the vertical group of the A-switchin the primary frame,

(s), the number of the secondary frame,

(d), the number of the D-switch in the secondary frame,

(n), the number of the connection in the horizontal group of theD-switch in the secondary frame,

(t), the number of the BC-conductor between the primary and secondaryframes, which number is also equal to the number of the B-switch in theprimary and the number of the C-switch in the secondary frame.

The line circuits are indicated by theindices p, a, m

and hence by LS p, a, m. The AB-conductors are indicated by the indicesp, a, t and hence by AB p, a, t. A vertical connection to a B-switch hasthe same number as the index a of the conductor AB p, a, t which isconnected thereto, in other words the number of the vertical connectionindicates which A-switch is coupled to this connection. TheBC-conductors are indicated by the indices p, s, t and hence by HG p, s,t. A vertical connection to a C-switch has the same number as the indexp of the conductor BC p, s, t which is connected thereto, in

other words the number of the vertical connection indicates whichprimary frame is coupled to this connection.

The CD-conductors are indicated by the indices s, d, a!v

hence by CD .5, d, t. The number of the vertical connection of aD-switch is the same as the index t of the conductor CD s, d, t which isconnected thereto, in other words this number indicates which C-switchis coupled to this connection. The repeaters are indicated by theindices s, d, n and hence by 0V .9, d, n.

The particular structure of the network of connections makes it possiblein the above-described manner to describe the connecting paths throughthe network between a given line circuit LS p, a, m and a given repeaterOV s, d, n with the indices of this line circuit and this repeater,hence with the indices p, a, m and s, d, n and an additional index 1which indicates the number of the relevant connecting path.

As previously described, the control portion of the A, B, C andD-switches includes a horizontal and a vertical group of conductorswhich cross one another at a number of crossings equal to the product ofthe number of conductors in the two groups. The crossings are indicatedby K followed by the denomination of the relevant switch. The crossingsin the A-switches are indicated by the indices p, a, t, m and hence byKA p, a, t, m, in other words by the indices of the conductors AB p, a,t and the index m of the line circuit LS p, a, m,. The crossings in theB-switches are indicated by the index of the conductors BC p, s, tandthe index A of the conductors p, a, t and hence by KB p, s, t, a. Thecrossings in the C-switches are indicated by the indices of theconductors CD s, d, t and the index p of the conductors BC 17, s, t andhence by KC s, d, t, p. At last, the crossings in the D-switches areindicated by the indices of the repeaters 0V s, d, n and the index I ofthe conductors CD .9, d, t and hence by RD S, d, n, t.

Each crossing between a conductor of a horizontal group and a conductorof a vertical group has associated with it the series-combination of arelay winding and a contact controlled by the relay, the relay includingtwo or more further contacts (not shown) for switching through the linewires and any additional conductors. The series-combination is connectedthrough the relay winding to the conductor of the horizontal group andthrough the contact of the relay to the conductor of the vertical group.Thus, in a connecting path between a given repeater 0V and a given linecircuit LS, the repeater, the CD, BC and AB-conductors located in theconnecting path and the line circuit are connected together through theseries-combination of a relay winding and a contact controlled by therelay. A relay winding is indicated in the figures by R followed by thedenomination of the switch and the contact of the relay is indicated bysmall letters. To distinguish between the various relays in thedescription, the indication in the figures is followed by the indicescorresponding to the relevant crossing. These indices are omitted in thefigures for the sake of clarity.

The common point between a relay winding and a contact controlled by arelay is connected to a marking conductor through a unidirectionallyconductive element, for example a diode, as shown in the drawings. In aprimary frame the crossings of the A-switches having the same index mare connected through individual diodes to a common marking conductorML, which is indicated and which thus give access to the same primaryframe are connected through diodes to the common marking conductor MB s,p. At last, the crossings of the D- switches having the same index 1 andwhich thus give access to the same C-switch are connected throughindividual diodes to a common marking conductor MC s, t.

In this connection it should be noted that, in order to reduce thenumber of marking conductors, the marking conductors ML p, m; MA p, a;MB s, p; MC s, t,

which have the same second indices m, a, p, t respectively, may beconnected together sothat the use of the marking conductors ML m, MA a,MB p and MC t suflices. Thus, in the example, the marking conductors MLand ML may be connected together, as well as ML12 and M1422, MA11 andMA21, and MC12 and MC22.

To build up a connecting path between a given repeater and a given linecircuit, the relays located in this connecting path have to beenergized. A connecting path is established by means of a marker ormarking element (not shown) which for this purpose has the disposal ofthe characteristic data of the repeater, namely the numbers s, d, n andthe characteristic data of the line circuit, namely the numbers p, a, m.As previously described, the connecting path between the given repeaterand the given line circuit is completely determined by said six indicesexcept for the value of the index i, which index indicates the number ofthe connecting path. In a manner similar to the test method known fromthe crossbar switch system No. 5 (crossbar No. 5), the marker testswhich AB, BC and CD-conductors located in the connecting paths enteringinto account are free. A free conductor is characterized by the absenceof a voltage or current on this conductor, whereas a busy conductor ischaracterized by the presence of a voltage or current. For example, themarker tests all the CD- conductors having the same indices s and d andhence all the conductors indicated by CD s, d, in other words the markertests all the CD-conductors which are connected to the relevant D-switchin the secondary frame and selects the free conductors. Similarly, themarker tests all the AB-conductors having the same indices p and a andhence all the AB-conductors which are connected to the relevant A-switchin the primary frame, which conductors are indicated by AB p, a, andselects the free conductors. The third index of the AB and CD-conductorsis the index t. From each test follow certain values for this index,these values indicating which of the tested conductors AB 12, a and Cds, d respectively are free. The marker then selects those values of theindex t for which an AB-conductor as well as a CD- conductor are freeand tests by these values of the index t whether a conductor BC p, s, tis free. After a free BC-conductor has been found, the index I is alsofixed and the connecting path completely determined.

In the case assumed in this example, in which a connecting path must bebuilt up between the repeater OV112 and the line circuit LSIIZ, themarker tests the conductors CD11 and the conductors AB11 and selectsthat value of the index 1 for which a CD-conductor as well as an AB-condnctor is free, for example the value t=2, and then tests thecondition of conductor BC112. The connecting path thus selected isindicated by thick lines. The values of the indices are in this casep=1, a=1, m=2, s: l, d: 1, n=2, t=2.

In the selected connecting path the relays RD s, d, n, t; RC s, d, t, p;RB p, s, t, a and RA p, a, t, m must be energized. To this end, themarker marks all the crossings which are connected to the markingconductors MC s, t; MB s, p; MA p, a; ML 2, m and the repeater OV s, d,n. The portion of the repeater which is important in this example isshown in the figure and comprises the seriescombination of a makecontact m and a resistor W bridged by a break contact he, whichseriescombination is connected to the negative terminal of a battery(not shown) having a voltage of, for example 48 volts. A repeater ismarked by closing the mcontact so that a voltage of 48 volts is set upacross the relevant horizontal connection of the D-switch. To

mark the marking. conductors selected, the marker applies a voltage of,for example 38 volts to marking conductor MC, a voltage of -28 volts tomarking conductor MB, a voltage of 18 voltsv to marking conductor MA,and a voltage of 8 volts to marking conductor ML. In the case underconsideration, the marker applies marking voltages of the specifiedvalues to the marking conductors MC12, MBll, MA11, ML12 and closes thecontact m in the repeater OV112. The relay windings RD1122, RC1121,RB1121 and RA1122, located in the connecting path and indicated by thicklines, are now successively energized, starting with relay RD1122. Thedifference voltage of +10 volts set up by marking conductor MC12 andrepeater OV112 across the series-combination of a diode and the relaywinding RD1122 and active in the forward direction of the diodeenergizes the relay which then closes the contact rd which is connectedin series with the relay winding. Conductor CD112 thus acquires avoltage equal to the voltage of marking conductor MC12 and hence avoltage of 38 volts. The difference voltage applied by conductor CD112and marking conductor MBll across the seriescombination of a diode andthe winding of relay RC1121 energizes this relay which then closes thecontact rc which is connected in series with the relay winding,resulting in conductor B112 acquiring a voltage equal to that of markingconductor MC11 and hence a voltage of 28 volts. The difference voltageactive between conductor BC112. and marking conductor MA11 thenenergizes the relay RBllZl, resulting in conductor AB112 acquiring viathe relay contact rb a voltage equal to that or marking conductor MA11and hence a voltage of l8 volts. At last, the difference voltage activebetween conductor AB112 and marking conductor ML12 energizes the relayRA1122, which then closes the relay contact ra. In the line circuits thevertical connections of the A-switches are connected through the dottedconnections to a point of constant potential, for example to ground. Assoon as relay RA1122 is energized the marker removes the markingvoltages from the marking conductors and the break contact he in therepeater OV112 is opened, resulting in resistor W being included inseries-combination in the selected connecting path. The value ofresistor W is adjusted so that the voltage on the horizontal connectionof the D-switch becomes smaller in absolute value than the markingvoltage applied to the marking conductors MC during marking and thatalso the voltage of the CD-conductor, the BC-conductor and theAB-conductor respectively becomes lower in absolute value than themarking voltage of the marking conductors MB, the marking conductors MAand the marking conductors ML respectively. For example, the voltage onthe horizontal connection of the D-switch is adjusted to -24 volts, sothat the CD-conductor, the BC-conductor and the AB-conductor acquirevoltages of 18 volts, 12 volts and 6 volts, respectively, which voltagesare lower in absolute value than the marking voltages of the saidmarking conductors, which are '38 volts, -28 volts, 18 volts and 8 voltsrespectively. The voltage drop across a relay winding is 10 volts duringthe marking of a connecting path and the voltage decreases to 6 voltsafter switching in the resistor W, which voltage suffices for keepingthe relay energized.

In the described manner the relay windings included in a connecting pathin series with an m-contact included in the repeater are kept energizedthrough the same windings which are used for energizing the relays sothat in the specified arrangement an additional holding winding and anadditional holding contact may be economized at each crossing of aswitch. Such an economy is considerable in communication networks of avolume that occurs in practice and also results in a greatly simplifiedstructure of the network.

In the arrangement described it is also realized that the diodes whichare connected in each case through a relay winding to either theconnection of a repeater the CD, BC and AB-conductors located in aconnecting path already built up, such as the diodes at the crossingsKD1121, KC1122, KB1122 and KA1121 in the example shown, when markingvoltages are applied to the marking conductors MC11, MB12, MA12 and ML11connected to these diodes, are controlled into the cut-01f direction bythe difieren-ce voltage between marking conductor MC11 and repeaterconnection OV112, between marking conductor MB12 and conductor CD112,between marking conductor MA12 and conductor BC112, and between markingconductor ML11 and conductor AB112 respectively, so that doubleconnections during building up of another connection cannot occur.

What is claimed is:

1. .An automatic switching network comprising a first group ofterminals, :1 second group of terminals, a. plurality of switchingstages, and a plurality of conductors interconnecting said terminals andswitching stages to provide a plurality of channels between any terminalof said first group and any terminal of said second group, each channelextending through each switching stage, each switching stage comprisinga plurality of crosspoint switch means, each crosspoint switch meanscomprising diodev means and a relay having a winding and a pair ofcontacts, each said stage having marker conductor means, means seriallyconnecting said diode means and winding between said marker conductormeans and a conductor extending toward said first group of terminalsfrom the respective stage, and means connecting each pair of relaycontacts between the junction of the diode and winding of the respectiverelay and a conductor extending toward said second group of terminalsfrom the respective stage, means for selectively applying markingpotentials between one terminal of said first group and a markingconductor of each stage, whereby a relay of each stage is energized byway of the diode means connected thereto for closing the respectivecontacts to establish a conductive path between said one terminal ofsaid first group and one terminal of said second group, and means forproviding a holding potential between said one terminal of said firstgroup and said one terminal of said second group whereby the diode meansconnected to said energized relays are reverse biased upon applicationof marking potentials between another terminal of said first group andsaid marking conductors of each stage.

2. An automatic switching network comprising a first group of terminals,a second group of terminals, a plurality of switching stagessequentially arranged between said first and second groups of terminals,each switching stage comprising a plurality of cross-point switch meansand having at least one marking conductor, a plurality of channelconductors interconnecting said terminals of said first group, saidswitching stages and terminals of said second group, whereby a pluralityof channels are provided between any terminal of said first group andany terminal of said second group by way of a cross-point switch meansof each stage, the cross-point switch means in each said stagecorresponding to a channel between a terminal of said first group and aterminal of said second group comprising a relay having a winding and apair of contacts, diode means, means serially connecting said diodemeans and winding in that order between a marking conductor and achannel conductor extending toward said terminal of said second group,and means connecting said contacts between the junction of said windingand diode means and a channel conductor extending toward said terminalof said first group, means for connecting said terminal of said firstgroup to a point of constant potential, means for applying a firstpotential differing from said constant potential to said terminal ofsaid second group, means for applying marking potentials diflering fromsaid first potential to marking conductors of said switching stageswhereby the relays corresponding to said channel are energized by way ofthe respective diode means to establish a conducting path between saidterminal of said first group and said terminal of said second group byway of the contacts and relay windings of the relays corresponding tosaid channel, and means for changing the potential at said terminal ofsaid second group to a second potential whereby the diode meanscorresponding to said channel are cut off upon subsequent application ofsaid marking potential to said marking conductors, the voltagedilference between said constant and first potential and between saidconstant and second potential being sufiicient to hold saidcorresponding relays energized.

No references cited.

KATHLEEN H. CLAFFY, Primary Examiner.

WILLIAM C. COOPER, Examiner.

1. AN AUTOMATIC SWITCHING NETWORK COMPRISING A FIRST GROUP OF TERMINALS,A SECOND GROUP OF TERMINALS, A PLURALITY OF SWITCHING STAGES, AND APLURALITY OF CONDUCTORS INTERCONNECTING SAID TERMINALS AND SWITCHINGSTAGES TO PROVIDE A PLURALITY OF CHANNELS BETWEEN ANY TERMINAL OF SAIDFIRST GROUP AND ANY TERMINAL OF SAID SECOND GROUP, EACH CHANNELEXTENDING THROUGH EACH SWITCHING STAGE, EACH SWITCHING STAGE COMPRISINGA PLURALITY OF CROSSPOINT SWITCH MEANS, EACH CROSSPOINT SWITCH MEANSCOMPRISING DIODE MEANS AND A RELAY HAVING A WINDING AND A PAIR OFCONTACTS, EACH SAID STAGE HAVING MARKER CONDUCTOR MEANS, MEANS SERIALLYCONNECTING SAID DIODE MEANS AND WINDING BETWEEN SAID MARKET CONDUCTORMEANS AND CONDUCTOR EXTENDING TOWARD SAID FIRST GROUP OF TERMINALS FROMTHE RESPECTIVE STAGE, AND MEANS CONNECTING EACH PAIR OF RELAY CONTACTSBETWEEN THE JUNCTION OF THE DIODE AND WINDING OF THE RESPECTIVE RELAYAND A CONDUCTOR EXTENDING TOWARD SAID SECOND GROUP OF TERMINALS FROM THERESPECTIVE STAGE, MEANS FOR SELECTIVELY APPLYING MARKING POTENTIALSBETWEEN ONE TERMINAL OF SAID FIRST GROUP AND A MARKING CONDUCTOR OF EACHSTAGE, WHEREBY A RELAY OF EACH STAGE IS ENERGIZED BY WAY OF THE DIODEMEANS CONNECTED THERETO FOR CLOSING THE RESPECTIVE CONTACTS TO ESTABLISHA CONDUCTIVE PATH BETWEEN SAID ONE TERMINAL OF SAID FIRST GROUP AND ONETERMINAL OF SAID SAECOND GROUP, AND MEANS FOR PROVIDING A HOLDINGPOTENTIAL BETWEN SAID ONE TERMINAL OF SAID FIRST GROUP AND SAID ONETERMINAL OF SAID SECOND GROUP WHEREBY THE DIODE MEANS CONNECTED TO SAIDENERGIZED RELAYS ARE REVERSE BIASED UPON APPLICATION OF MARKINGPOTENTIALS BETWEEN ANOTHER TERMINAL OF SAID FIRST GROUP AND SAID MARKINGCONDUCTORS OF EACH STAGE.